1. Field of the Invention
The present invention relates to a light-emitting device and a method for manufacturing the same.
2. Description of the Related Art
Light-emitting devices using a light-emitting diode have the advantages of energy conservation and long service life and have come to attract attention as a light source of a lighting apparatus, a color image display device, a backlight of a liquid crystal panel, a traffic light or the like.
Regarding such a light-emitting device, for example, Japanese Unexamined Patent Application Publication No. 2006-114820 discloses a light-emitting element in which a transparent crystal substrate, a pair of semiconductor layers comprising p-type and n-type nitride semiconductors, semiconductor surface electrodes for supplying a current to the pair of semiconductor layers and an insulating substrate are stacked in order. The insulating substrate has vertical conductors. The vertical conductor is formed within a vertical hole passing through the insulating substrate in a thickness direction by a plating process or a process of filling a conductive paste such as solder, whereby the semiconductor surface electrodes are electrically connected to mounting surface electrodes formed on the other side of the insulating substrate.
In the meantime, since the mounting surface electrodes are provided on a surface of the insulating substrate opposite from its light-emitting surface, the light-emitting element disclosed in Japanese Unexamined Patent Application Publication No. 2006-114820 has to be handled in the same manner as elements to be mounted on a surface of a printed circuit board.
However, since such a light-emitting element has an ultrathin structure typically having a thickness of about 20 μm, it is difficult to handle the light-emitting element like other elements to be mounted on a surface of a printed circuit board as in Japanese Unexamined Patent Application Publication No. 2006-114820. If the light-emitting element is broken by failure of handling in surface mounting, for example, the lighting apparatus or the like becomes less reliable.
When the vertical conductor is formed by a plating process, as disclosed in Japanese Unexamined Patent Application Publication No. 2006-114820, moreover, since the plating process inevitably needs a certain period of time, its production efficiency becomes extremely low.
On the other hand, when the vertical conductor is formed by a process of filling a conductive paste such as solder, the conductive paste filled into the vertical hole inevitably shrinks upon solidification to create a shrinkage cavity in the vertical conductor. Such a shrinkage cavity leads to increasing electrical resistance, deteriorating high-frequency characteristics and lowering reliability.